Fuel cell systems include a fuel cell stack that produces electrical energy based on a reaction between a hydrogen-based feed gas (e.g., pure hydrogen or a hydrogen reformate) and an oxidant feed gas (e.g., pure oxygen or oxygen-containing air). The hydrogen-based feed gas and oxidant feed gas are supplied to the fuel cell stack at appropriate operating conditions (i.e., temperature and pressure) for reacting therein. The proper conditioning of the feed gases is achieved by other components of the fuel cell stack to provide the proper operating conditions.
The fuel cell system includes a cooling system that maintains the fuel cell stack at a desired operating temperature. Generally, this temperature is approximately 80° C. The cooling system is in fluid communication with the fuel cell stack and typically includes a coolant reservoir, a pump and a heat exchanger. Coolant from the reservoir is circulated through the fuel cell stack by the pump. The warm coolant exiting the fuel cell stack flows through the heat exchanger, which enables heat dissipation to atmosphere to cool the coolant. The coolant flows back into the reservoir and is again circulated through the cooling system.
As the coolant flows through the fuel cell stack, it is in heat exchange relationship with the components of the fuel cell stack. In this manner, the coolant draws heat from the warmer components to regulate the temperature of the fuel cell stack. In some instances, the coolant is separated from the hydrogen-based feed gas flowing through the fuel cell stack by gaskets. The gaskets within the fuel cell stack do not provide a complete seal. As a result, hydrogen leakage can occur, whereby hydrogen leaks into the coolant. Additionally, hydrogen leaks can occur in other areas of the fuel cell system increasing the hydrogen content of the coolant. Eventually, the hydrogen content of the coolant achieves an undesirable level.